1. Field of the Invention
The present invention relates to an image reading apparatus. The present invention also relates to a light-leading member advantageously used in an image reading apparatus.
2. Description of the Related Art
An example of conventional image reading apparatus is disclosed in JP-A-6-217084. Referring to FIGS. 38 and 39 of the accompanying drawings, the conventional image reading apparatus (Ae) includes a lighting unit B accommodated in a housing 4e for illuminating a document paper sheet K, a glass plate 91 supported by the housing 4e, and a lens array 51e for focusing image-carrying reflection light coming from a reading section 90 of the image reading apparatus Ae. The image reading apparatus Ae also includes a plurality of image sensor chips 52e (only one is shown) mounted on a printed circuit board 6e.
As best shown in FIG. 39, the conventional lighting unit B includes a transparent, elongated light-leading member 1e and a light source 2e such as an LED (light emitting diode) carried by an additional printed circuit board 92. The light-leading member 1e includes an upper surface 12e, a lower surfaces 14e opposite to the upper surface 12e, two end surface 15e-16e, and so forth. The upper surface 12e is directed toward the reading section 90.
The light source 2e is arranged in facing relation to the end surface 15e. Thus, the light rays emitted from the light source 2e enter the light-leading member 1e at the end surface 15e to propagate through the light-leading member 1e toward the other end surface 16e. The light rays within the light-leading member 1e may be internally reflected several times by the upper surface 12e, the lower surface 14e and so forth, before the light rays come out through the upper surface 12e for illuminating the document paper sheet K.
The conventional image reading apparatus Ae has been found disadvantageous in the following points.
As stated above, two separate printed circuit boards (6e and 92) are used for the conventional image reading apparatus Ae. This means that it is necessary to form wiring patterns separately for the two circuit boards 6e and 92, which is time-consuming. In addition, the housing 4e should be arranged to accommodate the two circuit boards 6e and 92 at different positions. Such an arrangement may make the manufacturing of the housing 4e complicated.
Further, as shown in FIG. 38, side surfaces of the light-leading member 1e are exposed (i.e., the side surfaces are not covered by inner portions of the housing 4e or any other additional element.) Due to this arrangement, part of light propagating through the light-leading member 1e will unduly come out from the side surfaces, but not be used for illuminating the document paper sheet K.
Still further, even if the light propagating through the light-leading member 1e comes out through the upper surface 12e, the light may be directed in other directions but not toward the reading section 90.